1. Field of the Invention
This invention relates to a process of graphitizing carbon bodies, which are arranged with adjacent end faces of said carbon bodies adjoining each other and are clamped together to form a horizontal train, which is moved through a graphitizing furnace, in which the train is heated by a supply of electric current in a graphitizing zone containing a protective gas atmosphere and is subsequently cooled in a cooling zone. In dependence on the movement of said train through the graphitizing furnace, the train is continually supplemented at the entrance of the furnace in that individual carbon bodies are added to the train, and is continually shortened at the exit of the furnace in that individual carbon bodies are removed from the train. The invention relates also to an apparatus for carrying out the process.
2. Description of the Prior Art
Prefired carbon bodies which are to be graphitized are assembled in a train, in which adjacent end faces of the carbon bodies adjoin each other, and in said train are heated to the required graphitizing temperature by means of electric current which is caused to flow through a length portion of the train. In order to ensure that the graphitizing process can continuously be performed, the train is conveyed through a graphitizing furnace in conveying steps and after each conveying step a carbon body to be graphitized is added to the train at the entrance of the furnace and a graphitized carbon body is removed from the train at the same time at the exit of the furnace. Graphitizing furnaces which are particularly suitable for such a continuous graphitization of carbon bodies which engage each other at adjoining end faces have a horizontal furnace axis although this requires that the horizontally moving train is properly supported. For that purpose it is known to fill the graphitizing furnace with carbonaceous bulk material, such as coke or soot, which will provide the necessary support for the train of carbon bodies and will also avoid the presence of an oxidizing atmosphere in the furnace. But the use of such bulk material has the disadvantage that it must necessarily be heated in the graphitizing zone together with carbon bodies which are to be graphitized so that more energy will be required. Besides, a temperature rise of the carbonaceous bulk material will improve its electrical conductivity so that creepage currents conducted parallel to the train may occur.
In order to avoid said disadvantages it has already been proposed (Austrian Patent Specification 389,506 and the corresponding U.S. Pat. No. 4,956,849) not to fill the graphitizing furnace with carbonaceous bulk material but to provide in the graphitizing furnace a protective gas atmosphere and to axially clamp the train sufficiently to render it self-supporting. Whereas that measure will avoid the disadvantages involved in the use of carbonaceous bulk material, it will be necessary in that case to exert on the train considerable clamping forces in order to render the train self-supporting and the required magnitude of said clamping forces will depend on the length of the train and must even be maintained as a new carbon body is added to the train and a graphitized carbon body is removed from the train so that the structural expenditure will additionally be increased.